Most electrical systems are digital today and hence require analog-to-digital converters (ADCs) to interface to the outside world. The outside world can either be real world signals such as temperature, pressure, voice, etc., or modulated carriers transmitting information over some medium (analog or digital communication). For all applications, energy efficiency is extremely important and more so for battery operated systems.
Delta sigma modulators are widely used for high resolution, low speed ADCs as well as for medium resolution, high speed ADCs. Delta sigma modulators have high dynamic range which makes them robust for communication and signal processing areas. It is important to use a multi-bit delta sigma modulator to fulfill demand for higher resolution, wider bandwidth and low quantization noise power. A digital to analog converter (DAC) is used in a feedback path of the delta sigma modulator. The DAC includes multiple DAC elements. A major drawback of the multi-bit delta sigma modulator is non-linearity stemming from the mismatching between the DAC elements.
The mismatching between the DAC elements can be due to manufacturing variations, material imperfections, process, voltage and temperature (PVT) variations and similar other factors. This mismatch causes non-linearity in the feedback path of the delta sigma modulator, and results in distortion and noise at an output of the delta sigma modulator.